3,706 research outputs found
Cluster structures within Fermionic Molecular Dynamics
The many-body states in an extended Fermionic Molecular Dynamics approach are
flexible enough to allow the description of nuclei with shell model nature as
well as nuclei with cluster and halo structures. Different many-body
configurations are obtained by minimizing the energy under constraints on
collective variables like radius, dipole, quadrupole and octupole deformations.
In the sense of the Generator Coordinate Method we perform variation after
projection and multiconfiguration calculations. The same effective interaction
derived from realistic interactions by means of the Unitary Correlation
Operator Method is used for all nuclei. Aspects of the shell model and cluster
nature of the ground and excited states of C12 are discussed. To understand
energies and radii of neutron-rich He isotopes the soft-dipole mode is found to
be important.Comment: 5 pages, proceedings of the 8th International conference on
Clustering Aspects of Nuclear Structure and Dynamics, Nov. 2003, Nara, Japan,
to be published in Nucl. Phys.
Improved VHF direction finding system
Direction finding device operating at very high frequencies requires a loop antenna, mechanical rotation, and large structures. The system is applicable to an unmanned configuration. Direction information is extracted in the form of a direction cosine analog
Space station experiment definition: Advanced power system test bed
A conceptual design for an advanced photovoltaic power system test bed was provided and the requirements for advanced photovoltaic power system experiments better defined. Results of this study will be used in the design efforts conducted in phase B and phase C/D of the space station program so that the test bed capabilities will be responsive to user needs. Critical PV and energy storage technologies were identified and inputs were received from the idustry (government and commercial, U.S. and international) which identified experimental requirements. These inputs were used to develop a number of different conceptual designs. Pros and cons of each were discussed and a strawman candidate identified. A preliminary evolutionary plan, which included necessary precursor activities, was established and cost estimates presented which would allow for a successful implementation to the space station in the 1994 time frame
String breaking with dynamical Wilson fermions
We present results of our ongoing determination of string breaking in full
QCD with N_f=2 Wilson fermions. Our investigation of the fission of the static
quark-antiquark string into a static-light meson-antimeson system is based on
dynamical configurations of size 24^3 x 40 produced by the TxL collaboration.
Combining various optimization methods we determine the matrix elements of the
two-by-two system with so far unprecedented accuracy. The all-to-all light
quark propagators occurring in the transition element are computed from
eigenmodes of the Hermitian Wilson-Dirac matrix complemented by stochastic
estimates in the orthogonal subspace. We observe a clear signature for
level-splitting between ground state and excited potential. Thus, for the first
time, string breaking induced by sea quarks is observed in a simulation of
4-dimensional lattice-QCD.Comment: 3 pages, 3 figures, contribution to Lattice 200
A Supernova Factory in the Merger System Arp 299
We have imaged the nearby galaxy merger Arp 299 at arcsecond and
milliarcsecond resolution, using both the Very Large Array and the Very Long
Baseline Array. The large-scale radio emission from the merger contains 5
bright, compact radio sources embedded in diffuse emission, with diameters less
than 200 pc. Supernova rates of 0.1 to 1 per year are required to produce the
VLA-detected radio emission in these sources. Two of the compact VLA radio
sources, designated Source A and Source D, also have been detected and imaged
at milliarcsecond scales. Source A, which is associated with the nucleus of one
of the merging galaxies, contains five milliarcsecond-scale sources, each with
a radio power between 100 and 1000 times that of the Galactic supernova remnant
Cassiopeia A. Four of these have flat or inverted spectra and appear to be
young supernovae. Three of the VLBI-scale sources are located within 10 pc
(projected) of one another, and two are separated by less than 3 pc, indicating
that they all may be within the same super starcluster or complex of such
clusters. The brightest VLBI-scale source, A0, has an extremely inverted
pectrum, with alpha larger than +2 at gigahertz frequencies. It seems to be the
youngest supernova, which has not yet broken out of its circumstellar shell.
The milliarcsecond radio sources within Source A appear to constitute a
upernova factory, confirming the presence of an extreme starburst that peaked
at least a few million years ago.Comment: Accepted for the Astrophysical Journal, 22 pages, 10 figure
U.S. Foreign Direct Investment in the Western Hemisphere Processed Food Industry
Foreign direct investment (FDI) has become the leading means for U.S. processed food companies to participate in international markets. Affiliates of U.S.-owned food processing companies had $30 billion in sales throughout the Western Hemisphere in 1995, nearly 4 times the level of processed food exports. This report puts U.S. foreign direct investment and trade in processed foods to the region into global perspective, and finds evidence that, in the aggregate for the 1990's, trade and FDI are complementary--not competitive--means of accessing international food markets. Incomes have grown sufficiently in most countries to support growth in affiliate sales and U.S. exports, indicating a strong demand for a wide variety of processed foods.U.S. food processing industry, Western Hemisphere, foreign trade, foreign direct investment, Agribusiness, International Relations/Trade,
- …